Thanks to the people who have posted suggestions to help debug my problem.

I have had some success. The problem that I have described is occuring in a network where I have physical access to all of the computers. So, during the process of debugging it on those machines, I have been using the same account that I used when I created the program.

This is an interim report. I need to do more checking.

I was able to get the program running without error on one of the machines where it previously did not run without errors. I reported earlier that when I made one change the originally problem disappeared, and a different error appeared in a different method of the same object, the TxtBtns group of buttons from the WizBtns.vcx library that ships with VFP. When I examined this second error more closely, I discovered that there was an error in the code for the TxtBtns.Destroy() method.And, this error is what I was seeing. The TxtBtns.Destroy method loops through all of the cursors of the data environment, and reverts all tables that are open and buffered. It uses an IF statement to identify the members of the DE that are cursors. However, the IF statement begins with: IF USED(.ALIAS) AND ATC("CURSOR", .BaseClass)#0...

But, the DE also contains relations, and so, when the loop gets to the relations in the DE, the USED(.ALIAS) clause fails since relations don't have aliases. I just reveresed the order of these two clauses, and the error in the Destroy() method went away.

This raises a new question: I have been using these buttons for years. Why has this error not occurred before?

Thanks again for your help. I will provide another report when I have had a chance to test this "solution" more.

Jim